1. Field of the Invention
The present invention relates to configurable circuits and more particularly concerns circuits that can be electrically configured and re-configured.
2. Description of Related Art
Many electronic circuits, including circuit boards and entire electronic systems, must be trimmed and configured either upon completion of manufacture, at installation or after some time of use. Often circuit components will drift due to aging or environmental factors, and thus need be adjusted for proper operation. Other circuits require such adjustments in order to alter operation and function of the circuit. Thus it is frequently desirable to selectively vary or adjust such circuit operations and parameters as frequency, resistance, capacitance, switch selection and data line selections. Presently trimming and configuration or reconfiguration of such circuits and system is accomplished by use of mechanical DIP switches and potentiometers, or sometimes by laser trimming of circuit components. These methods are slow or may require expensive equipment. Mechanical trimming switches, potentiometers and the like are expensive, relatively difficult to build and assemble, require physical access to the device and are inherently less reliable than electronic components. Laser trimming equipment is expensive and is generally available only upon manufacture of circuitry, and cannot be accomplished in the field.
Circuits have been programmed by use of EEPROM memories, but such prior art is able to handle configuration of several circuits only with great complexity and increased numbers of control lines. Prior arrangements, furthermore, make no provisions for digital readout of the actual configuration of the device, and, moreover, have been available only for a configurable potentiometer or an array of resistors.
Where circuit boards or systems operate in environments or packages that make access difficult, or where such circuits or devices are encapsulated, the circuit boards and systems may require trimming, adjustment or other reconfiguration which cannot be accomplished in presently available mechanical systems.
Accordingly, it is an object of the present invention to provide configurable circuits that avoid or minimize above mentioned problems.